Merck board approves repurchase of $10 billion more in stock

Merck & Co. says its board approved the repurchase of up to $10 billion more of its stock.

The drugmaker said Tuesday that amount will be added to the $1.7 billion remaining available for repurchase under a prior authorization.

Investors cheer stock buybacks because they reduce the number of shares in circulation, making them more valuable. Fewer shares outstanding also means more earnings per share.

Shares of the Kenilworth, New Jersey-based company rose 86 cents, or 1.5 percent, to $59.49 in aftermarket trading following the buyback announcement. Through the close of Tuesday's regular trading session, the stock has gained about 9 percent in the past year.